The present invention relates to automated workpiece handling devices which clampingly grip and transfer workpieces from one station to another during manufacturing and/or assembly operations.
Automated workpiece handling devices (also known as xe2x80x9cgrippersxe2x80x9d) are widely employed, typically in the automotive industry, and typically include a fluid pressure-actuated mechanism with one or more gripper jaw members. The fluid pressure actuated mechanism is typically a pneumatic or hydraulic differential motor or the like and is mounted on a robot or other type of workpiece handling or transfer mechanism. One or more moveable gripper jaws are pivotally mounted to a piston rod operated by the fluid pressure actuated mechanism.
When the piston is moved in one direction, the jaws are pivoted to an open position. Upon movement of the piston in the opposite direction, the jaws are driven to a closed workpiece gripping position. These devices are typically utilized to transfer a workpiece in an assembly line or manufacturing operation from one station to another.
In typical operation, the gripper jaws are closed upon a workpiece near or adjacent an edge of the workpiece and the gripper itself is then moved in order to reposition the gripped workpiece in, for example, an adjacent workstation. The gripper is opened at the subsequent workstation to release the workpiece and the process is repeated for subsequent workpieces. In this regard, at the conclusion of the work operation, the gripper device repositions itself back into its initial workstation and the jaws are again activated to close and grip upon a subsequent workpiece and carry it away in the same manner. Opening and closing the gripper jaws takes place when the gripper device is in the closest proximity to the tooling at the workstation.
Known types of linkage arrangements used in fluid pressure actuated grippers to connect the gripper jaws to the piston rods and affect movement thereof are pivotal link arrangements and pivotal cam arrangements. Examples of these arrangements are found, for example, in U.S. Pat. Nos. 5,503,378, 5,152,568, 4,518,187, and 6,048,013.
In a typical production line, there are numerous workstations with one or more fluid pressure actuated gripper devices positioned adjacent or between workstations. During operation, the gripper devices are synchronized so that they simultaneously remove a workpiece from one workstation and transfer the work piece to the next workstation.
Problems can occur if one of the gripper devices fails to properly grip a workpiece and the workpiece slips out of alignment. Other problems can occur if the gripper does not open a sufficient amount in order to clear possible obstacles or satisfactory grip the workpiece, or if a workpiece is transferred in a misaligned manner and subsequently positioned at a workstation in a misaligned fashion. Such incidents can damage the workstation as well as the workpiece. Also, an automatic gripper device can completely lose grip on the workpiece if, for example, there is a leak or failure of the fluid pressure supplied to the actuator.
Fluid pressure actuated grippers are generally designed for use with particular workpieces to be transferred and with specific workstations. For example, some workpieces and workstations may require wider or narrower gripper jaws, different types of gripper jaws, gripper jaws that open at different angles, different clearance requirements, and the like. In many cases, it is important to have the gripper jaws opened as wide as possible, for example 70-90xc2x0, in order to satisfactorily grip the workpieces and move them from one workstation to another. It is also important for economic and assembly requirements to provide gripper devices with modular-type components.
Thus, it would be advantageous to provide a fluid pressure actuated gripper device in which the gripper devices have modular components, the gripper jaws can be easily changed and replaced, and the jaws can open to maximum width positions.
The present invention is directed to fluid pressure actuated gripper devices of the type employed in automated workpiece handling systems which clampingly grip and transfer workpieces from one station to another. The gripper devices of the present invention include a pneumatic or hydraulic cylinder (or xe2x80x9cmotorxe2x80x9d) which drives the piston rod in a reciprocal fashion, and a pair of gripper jaws which are operatively attached to the piston rod and affect opening and closing of at least one of the jaws as the piston rod undergoes reciprocal motion. The gripper device includes a base member which is attached to a pressure actuated cylinder and a pair of detachable side plate members. A pivotal cam-type linkage is utilized to open and close one or more of the jaw members. A pair of offset cam pins attached to the reciprocal piston rod member slide in grooves in the side plate members causing the jaw members to move and rotate around pivot members. Cam grooves in the gripper jaws have particular shapes which affects the amount of movement of the jaws and thus the opening and closing of the gripper devices. Pivot shafts or pin members operatively attached to the jaw members are positioned in blind openings in the side plate members and provide pivot axis for the jaw members to rotate when they are operated by the piston rod and cam pins. The pivot pin members can be positioned at various locations in said side plate members in order to preset or control the amount of pivoting of the jaw members and thus the amount of opening of the gripper jaw members. The two cam pins are axially offset from one another and allow the jaw members to open in an extended manner, up to 90xc2x0.
A number of components of the gripper device are also modular in that they can be replaced or interchanged with other components to change the degree of movement of the jaw members for different applications.
Alternative embodiments of the present invention include gripper devices in which only one jaw member is operable by the fluid pressure actuated mechanism while the other jaw member remains stationary. In addition, differently shaped cam slots on the jaw members can restrict the opening of the jaw members to various degrees of opening, as desired. Also, various types of gripper tips can be provided on the gripper jaws.